Most important click in your Facebook Privacy Settings

Let's face it, people change, attitudes shift, life is fluid. It just takes a single life event - a breakup, a divorce, a new job, a baby - and Facebook posts in your past, some you may have had no qualms displaying publicly on your profile, are suddenly things you'd rather keep to yourself and your friends.

These could be party photos from yesteryears, angry rants, old philosophical or political musings or personal associates you no longer want the whole world to know about.

In the early days of Facebook, rummaging through one's wall and past posts was cumbersome and time-consuming. A would-be stalker had to scroll through hundreds of chronologically arranged posts to look further and further in one's Facebook past. Only the most patient sleuths can ever manage to dig deep through a Facebook wall to uncover past shenanigans buried by time.

But things changed with the arrival of the Facebook Timeline and Graph Search a few years ago. With this approach, Facebook opened up its huge trove of user data and made it searchable and easily accessible - neatly divided into year and month. That old Facebook wall was turned into what is essentially a searchable book you could leaf through and navigate instantly.

Of course, while it's really quick and simple to specify the privacy of your future posts, it is understandably a daunting task to review the privacy of each and every post, photo, check-in, etc. you have accumulated in your Facebook past. And if you're a long-time prolific Facebook poster, this could prove nearly impossible.

Limit Past Posts

Thankfully, Facebook provides a way to lock down your Timeline and retroactively change the privacy settings of your past posts quickly with one click. Your unflattering photos and cringe-worthy posts from the past might be non-incriminating enough to share with your friends and relatives (they'll understand, right?) but may not be appropriate for perfect strangers (or future employers).

To lock down all your past posts marked as shared with "Friends of Friends" or "Public," navigate to this option:

On the Facebook site, at the top of the page, click the upside-down triangle and select Settings. On the mobile app (iOS or Android), tap the hamburger (three horizontal lines) icon to access your profile shortcuts then scroll down and tap "Settings" >> "Account Settings."

In this section, navigate to "Privacy" then under "Who can see my stuff?" you'll see a section that asks "Limit the audience for posts you've shared with friends of friends or Public?"

To instantly lock down every post you've done in the past to "Friends only," click the "Limit Old Posts."

Please be warned that this action is undoable! If you have public posts you are proud of and would want the whole world to see, you will have to go back and change the privacy setting for each post manually.

Also, if you've authorized others to tag you in past posts, the person who tagged you and the other people who were tagged in those posts will still be included in its audience. At this point, you will have to manually track down and review past tags via the Activity Log.

Keep in mind that this option will only protect your Facebook past from strangers. Anyone in your Friends list can still look up and search everything in your Facebook profile.

To hide a past post from both strangers and friends, you will have to search for the post yourself and either set its privacy to "Only me" or delete it from Facebook completely.